This invention relates to hydraulic rotary percussive machines of the kind used for rock drilling.
In such machines there is a percussion motor to impart percussive energy to a rock drill stem and means to rotate the drill stem chucked to the machine. In some machines the piston of the motor causes rotation through a ratchet mechanism and in that case a single hydraulic feed line and a single tank line are required. In other machines the rotation is achieved by means of a motor (which can take many forms) which rotates the chuck independently of the percussion motor.
With an independent rotation motor it is also customary to have an independent source of hydraulic fluid, e.g. by having a prime mover driving two pumps: one for the percussion motor and one for the rotation motor. This is done so that the rotation motor is not starved of motive power by the percussion motor. The duplication of pumps and the need for extra supply and return lines makes this a cumbersome and expensive arrangement.